Second-period goals by the Penguins' Shawn McEachern, Mario Lemieux and Kevin Stevens turned around a game that had looked like a continuation of the Capitals' Friday night dominance of the Patrick Division leaders.
The Capitals (10-13-2) had beaten the Penguins, 6-4, in extending their unbeaten streak to four games (3-0-1) Friday.
With a 4-3 lead, the Penguins (17-6-3) missed on two clear chances to establish control early in the third period. At the 6:50 mark, left wing Troy Loney was wide open on the right side of the net to accept McEachern's pass, but Loney's shot flew wide. Some three minutes later, defenseman Larry Murphy fanned on a slap shot after a breakaway pass from Lemieux.
The Capitals, though, hardly even threatened. Of their 12 third-period shots, only a back-hander by Kevin Hatcher with 3:30 left required more than a token effort by Pittsburgh goalie Tom Barrasso, who improved his record to 15-4-2.
The Penguins got the insurance they had been seeking when Lemieux scored his 29th goal on an empty-netter with 10 seconds left.
For getting so little accomplished during most of the second period, the Capitals had to be pleased to be trailing just 4-3 entering the final 20 minutes.
Right wing Peter Bondra scored his 14th goal on a power play by lifting the rebound of Al Iafrate's miss into the right-hand corner .. at 18:09, putting the Capitals back into a game that had rapidly slipped away. They had gone from two goals up to a two-goal deficit in less than 15 minutes.
It was nothing like that at the start. At 7:33 of the opening period, the Penguins' Ulf Samuelsson was penalized for cross-checking with the Penguins already one man short.
Only 33 seconds into the two-man advantage, Michal Pivonka wristed a shot from the right circle that was knocked clear by Barrasso, but Dimitri Khristich poked the rebound into the left side of the net.
Pittsburgh was at full strength when the Capitals made it 2-0. Defenseman Iafrate, who starred in Friday's victory, cleared a faceoff win to winger Kelly Miller at the left point. His slap shot was smacked out of the air and past Barrasso by Sylvain Cote at 9:36.
The Penguins began their comeback on the power play. Right wing Rick Tocchet established his position in the slot and turned a Murphy feed from behind the net into his 16th goal at 17:10 to cut the Capitals advantage to 2-1.
The loss of that lead just 1:24 into the second period caused goalie Don Beaupre to lose his cool. His reaction to what appeared to be a missed interference call drew a 10-minute misconduct penalty that had to be served by Paul Cavallini.
The lack of a penalty call meant Stevens was free to take the rebound of Murphy's slap shot and swat it past Beaupre for a 2-2 tie.
Beaupre was penalized a second time in the period for tripping at 12:12. The Penguins took advantage with Lemieux's power-play goal at 6:58. Ron Francis and Murphy were credited with assists, but this was a solo job created by Lemieux's 360-degree spin to his left and searing shot past Beaupre's stick.
Coach Terry Murray tried a goaltender change after that, opting for Jim Hrivnak, the man who had beaten the Penguins Friday.
Less than a minute later, though, Hrivnak was the victim of Jaromir Jagr's stick-handling ability. Jagr carried the puck from his own blue line, maneuvering past Cote and bouncing it off Calle Johansson in the crease. McEachern picked it up there and lifted it by Hrivnak for his 14th goal and a 4-2 lead.
Washington 2 1 0 -- 3
Pittsburgh 1 3 1 -- 5